The Drop Test,
from a regulated height.
One independent free-fall onto a steel anvil, recorded in slow motion. The single regulatory proxy for a forklift drop, a misjudged corner, a sliding pallet — and the single most common reason a 4G or 4GV fibreboard box loses its UN certification.
The single break point
between a certified box
and a leaking pallet.
The test, in one paragraph
A conditioned specimen, with its inner receptacles loaded to the agreed contents, is released from a fixed height onto a non-resilient horizontal surface. The drop is unsupported, the orientation is prescribed, and the impact is captured on slow-motion video. The specimen passes if the inner contents do not leak and any closures hold. The same test runs in five different orientations across a population of five samples — the box must survive all of them.
Why it’s the test that matters
For combination packagings — a fibreboard outer with inner receptacles — the drop test is the load case the regulators care about most. A box that absorbs a calibrated fall on its weakest corner without releasing its contents is a box that survives a forklift, a roller belt, a transfer hub. Every UN 4G mark on a fibreboard outer traces back, in part, to a successful run of this test under accredited conditions.
The height is set by the
most dangerous thing
you might put inside.
UN 6.1.5.3.4 indexes the drop height to the packing group the packaging is approved for — not the goods you happen to be shipping. Approve a box at PG II and you can ship anything classed PG II or below.
| Packing Group | Hazard Severity | Drop Height | Tolerance |
|---|---|---|---|
| PG I / great danger | High — e.g. anhydrous hydrazine, nitric acid ≥ 70% | 1.8m | ± 2 cm |
| PG II / medium danger | Medium — most flammable liquids, lithium-ion above threshold | 1.2m | ± 2 cm |
| PG III / minor danger | Lower — diesel, environmentally hazardous mixtures | 0.8m | ± 2 cm |
For large packagings — design type 50G — the heights of UN 6.6.5.3.4 apply and align with the values above. Where the goods are solids loaded to maximum mass, an additional tolerance applies. Combination packagings 4G and 4GV use this same table without modification.
Five drops,
five attitudes,
one verdict per box.
Each specimen is dropped once. The orientation set is prescribed in the certification programme and distributed across the five-sample population — so every box in the population sees a different attitude, and the box design is judged on the whole.
For corner drops on combination packagings the impact point is the lowest corner across the diagonal from the manufacturing joint — the corner most likely to break in transit. The same logic applies on edges for liquid-bearing inner receptacles: the impact edge is the closure-side edge of the manufacturing joint.
The box either
holds the contents,
or it doesn’t.
Calibrated.
Traceable.
Recorded.
- Drop tester
- Electromagnetic clean-release
- Verticality ≤ 1° over fall path
- Drop surface
- Steel anvil, ≥ 600 kg
- Level to ± 0.2° · smooth, non-resilient
- Conditioning room
- 23°C ± 2 / 50% RH ± 2
- ISO 2233 · 24 h minimum hold
- Capture
- Slow-motion video
- 240 fps minimum · archived with report
Five steps,
a single signed report,
and the slow-mo to prove it.
Each run produces a calibrated record of every drop — the height, the orientation, the impact frame, and the inspector’s observation, signed off under our BELAC scope.
Condition
Specimens held ≥ 24 h at 23 °C / 50% RH per ISO 2233 to normalise board moisture.
Load
Inner receptacles filled to agreed contents and mass; closures applied to the production specification.
Mount
Specimen aligned in the release jig at the prescribed orientation for that drop in the set.
Release
Free-fall from the packing-group height. Single drop, recorded at 240 fps minimum.
Inspect
Visual + sponge-blow inspection. Verdict recorded; specimen archived; footage attached to the report.
Most boxes that fail
fail in four predictable ways.
A drop test failure is rarely a surprise to the people who saw the slow-motion. The four patterns below cover the majority of unsuccessful runs — and each one points back to a different specification you can adjust before resubmission.
Joint adhesive release
Manufacturing joint opens on corner impact, releasing inner receptacles.
FIX » Adhesive grammage · Cure time
Edge burst
Board ruptures along the impact edge before energy dissipates to inners.
FIX » Edge crush spec · Flute grade
Inner-receptacle slip
Cushioning fails to retain inner; receptacle reorients on impact and breaches.
FIX » Cushioning density · Fitment
Closure detachment
Outer tape or strap separates on top-flat or corner drops, opening the box.
FIX » Closure spec · Width · Wrap
The drop test rarely
travels alone.
Stacking Test
Load applied for a 72-hour hold at controlled humidity — the warehouse storage that follows every successful drop.
Burst Resistance Test
Hydraulic pressure to rupture — the upstream board metric that explains why a corner blew on impact.
The questions
we hear
every quote.
Short answers below. For anything that doesn’t fit, a 10-minute call with Walter usually does.
How many specimens do you need for a drop programme?
For a combination packaging at a single packing group, the standard run is five specimens distributed across the prescribed orientations. For variant programmes — multiple inner receptacle weights, mixed loads, or designs straddling packing-group thresholds — the population scales accordingly. We confirm the count at the brief stage.
Are the drop heights the same for 4G and 4GV?
Yes. Both 4G and 4GV follow the heights set by UN 6.1.5.3.4 — 1.8 m for PG I, 1.2 m for PG II, 0.8 m for PG III. The differences between 4G and 4GV sit in inner-packaging variability, not in the drop programme itself.
If a specimen fails, does the whole certification fall over?
Not automatically. A single specimen failure ends that run, but a remediated design can be re-submitted. We document the failure mode in the report so the manufacturer knows exactly what to adjust — usually one of the four patterns on this page — before the next attempt.
What contents do you use for the inner receptacles?
The reference substance is water unless the certification target requires something more representative. For volatile or hazardous loads we use approved surrogate fluids of matched density and viscosity per UN 6.1.5.2.5. The substitution is recorded in the report.
How long does the slow-motion footage stay on file?
The signed report and its attached footage are archived under our BELAC quality system for the full certificate validity period and beyond — available on request from Walter or any successor signatory of the accredited laboratory.
Send us your box.
We’ll send you the slow-mo.
A short brief is enough to scope a drop test programme — we’ll confirm specimen count, orientations and packing group on the same call.